Across:
1 Supports those no longer working (OLD AGE PENSION) for gaoled (gaoled) criminal (= anagram indicator) (gaoled = OLD AGE) at nice boarding house ((Nice/French 'boarding house' = PENSION) (OLD AGE PENSION),
10 Doesn’t know what one is doing (LO-ST) securing type of blood (-B- blood group) in hospital (-ER) (LOBSTER) for crabby relative (LOBSTER),
11 An Eliot (an Eliot) novel (= anagram indicator) (an Eliot = TOENAIL) may need to be cut and polished (TOENAIL),
12 Dublin terrace (Dublin supporters’ terrace in Croke Park = HILL), a home for those in 3 down (a home for ‘ants’ = HILL),
13 Modernist dismisses miso (‘modernist’ dismisses ‘miso’ = dernt = TREND) – it’s just a craze (TREND),
15 Fragment of dispatch is statesman-like (fragment of ‘dispatcH IS Statesman-like’ = HISS) or so I heard at meeting of COBRA? (HISS),
17 The German (‘the’ German = das) Review (= reverse indicator) (das = SAD) is woeful (SAD),
19 Green light (GO-) for the greatest (Muhammad Ali = -ALI-) drug (-E) (GOALIE) employed as a last line of defence, in short (GOALIE),
21 Dug up (= reverse indicator) best (best/top = POT-) part of the forest (-ASH) (POTASH) for fertiliser (POTASH),
22 My tyres (my tyres) burst (= anagram indicator) (my tyres = MYSTERY)? Whodunnit! (MYSTERY)
23 Distort the sound coming from syrinx (GARBLE) of the Spanish (‘the’ Spanish = el = -LE) crow (brag = GARB-) making a comeback (= reverse indicator) (GARBLE),
25 Raising (= reversal indicator) zero (-O) tax (VAT = -TAV-) from firm (Co = OC-) (OCTAVO) is one for the books (OCTAVO),
27 Past one’s prime (OLD) starting for all sides today (OLD on all sides of today’s grid),
29 Groan out of arrogance (‘groan’ out of ‘arrogance’ = arce = RACE) in Irish, for example (RACE),
30 Lobby (FOYER) in favour of (FO-R) those in 20 down (eye) without a leader (e) (‘eye’ without ‘e’ = (-YE-) inside (FOYER),
31 Extract of what I mean (extract of ‘whaT I MEan’ = time) turns up (= reverse indicator) (time = EMIT) in issue (EMIT),
34 A (A-) retweet (-RT) last month (DEC-) from circle (-O) (ART DECO) employed in 1930s by stylists (ART DECO),
35 Organisation (UN-) is never (never) out (= anagram indicator) (never = -NERVE) (UNNERVE) to intimidate (UNNERVE),
36 Precious type (gold) heading off (g) (‘gold’ without ‘g’ = OLD) to River associated with Irish battle (Battle of the Boyne / River Boyne = BOY NE-)? The first (‘The first = -T-) job (-WORK) (OLD BOY NETWORK) for group of establishment types! (OLD BOY NETWORK).
Down:
2 Plant (LOBELIA) lots of broccoli heads ('Lots Of Broccoli' heads = LOB-) in spring (= anagram indicator)? A lie! (a lie = -ELIA) (LOBELIA),
3 Characters amidst gallant supporters (characters amidst ‘gallANT Supporters’ = ANTS) from The Hill (ANTS),
4 Mistakes (ERRORS) produced by those characters in the USSR or Republic (in ‘the usSR OR REpublic’ = srorre) going all the way back (= reversal indicator) (srorre = ERRORS),
5 Writer (ed = E-D) holds on to next (next) novel (= anagram indicator) (next = -XTEN-) (EXTEND) to make it longer (EXTEND),
6 Fat (SUET) deposit (deposit/put down = S-ET) around top of ulna (top of ‘Ulna’ = -U-) (SUET),
7 Instrument (OCARINA) in old (O-) auto (-CAR-) in (-IN-) America (-A) (OCARINA),
8 Elderly (OLD) stoned (HIGH) native of Munster (native of Münster in Germany = GERMAN)? (OLD HIGH GERMAN) In a manner of speaking, in the past! (OLD HIGH GERMAN),
9 Drunk (= anagram indicator) idle sot (idle sot = OLD TIES) consuming a number of fish (SCHOOL) (OLD SCHOOL TIES) out of group loyalty (OLD SCHOOL TIES),
14 Steer away from Harley Street (‘steer’ away from ‘Harley Street’ = harleyt = EARTHLY) – it’s not out of this world? (EARTHLY),
16 Papers (ID papers) reviewed (= reversal indicator) (ID papers = DI-) by Mike (-M-) only half (‘onLY’ half = -LY) (DIMLY) seen but not in the best light (DIMLY),
18 Great pleasure (JOY-) meeting Clare (-CE) (JOYCE), a writer synonymous with Dubliners (James JOYCE writer of Dubliners),
20 Sight (EYE) of some lamprey eels (some ‘lamprEY Eels’ = EYE),
21 One getting paid for play (PRO) is irate leaving Pretoria (‘irate’ leaving ‘Pretoria’ = pro = PRO),
24 Show (RECITAL) what is authentic (real = RE-AL) about unfinished (y) large conurbation (city) (‘city’ without ‘y’ = -CIT-) (RECITAL),
26 Bill (AD-) Marsh (marsh/swamp = -MIRE-) is writing (from the 3Rs = -R) (ADMIRER) to devotee (ADMIRER),
27 Gents (loo) getting up (= reverse indicator) (loo = OOL-) close to Furbo (close/end to ‘furbo’ = -O-) on the outskirts of Galway (outskirts of ‘GalwaY’ = -GY) (OOLOGY) for the study of birds’ eggs (OOLOGY),
28 Workout (work out = DEDUCE) for two of the clubs, for instance (two of clubs/playing cards = DE-UCE), around Dublin (-D-) (DEDUCE),
32 Part of sombre hotel set up (= reverse indicator) (part of ‘somBRE Hotel’ = breh = HERB) by Rosemary (HERB),
33 Recognised (KNEW) it sounds (= homophone indicator) modern? (‘new’ = ‘KNEW’).